Process optimization with Box-Behnken experimental design for photocatalytic degradation of thiamethoxam using perlite supported TiO2

Effective photocatalytic degradation of thiamethoxam (THX) at low concentration was achieved by using perlite supported TiO2 composite material (PST). Box-Behnken experimental design method was employed in order to evaluate the effect of process parameters and also optimize them. Accordingly, effects of three process parameters (pH, load of PST [PT {g/L}], and air flow rate [AF {L/h}]) were investigated on two responses: (i) the THX degradation percentage after 270 min (DEG270 [%]) and (ii) the electric energy per order (EE/O [kWh/m(3)]). THX degradation was improved by decreasing pH value and increasing air flow rate. Increasing load of PST increased the degradation percentage until a critical value of about 8 g/L, then caused a decrease. Statistically significant second-order polynomial models were developed by regression analysis of experimental data. Optimum conditions were obtained as follows: pH 4, PT 8.30 g/L and AF 18 L/h for an initial THX concentration of 1.46 ppm. These conditions led to a response of 87% +/- 5% for DEG270 and 120 +/- 21 kWh/m(3) for EE/O. Control experiments confirmed a good optimized process and reusability of PST without any regeneration step.